Any place you can make a setting for the throttle curve would work but this is an ease of use change. I would make sure to fix any real problem before putting a curve on throttle. When making a throttle curve you need to make sure that zero throttle stick still means zero throttle, or you can't arm, etc. GCS Vehicle page has a throttle curve where you could set it too.

Another thing I forgot about: One set of many cheap eBay ESCs came with old firmware and did exactly this; jump up with low throttle and sometimes require shutting motors completely off at zero throttle to get it to come back down. Flashing the latest firmware immediately fixed the problem. Now days when I buy cheap ESCs I first test for dead in case they need to be sent back for a refund (never happened yet). I always flash the latest firmware before installing them. This system works well for me.

Watching again all the videos I see that it is stabilizing and that is good. You know how to successfully control throttle and that is good. How much throttle stick does it take to lift off? Less than one fourth?

The other quads that you have flown, did they have a spring on the throttle stick? Did they have sensors to help you control the altitude? Flying without altitude sensors needs very small corrections on the throttle stick. Forgive me for saying, because I don't know your experience. You can't just set the throttle stick to the middle and expect it to hover. You must find the place where the power is correct for hover. Sorry if you know this already, but I can't tell how much throttle stick you are giving.

1mm is the difference between climbing slowly and descending slowly. Moving the stick down 10mm from hover power makes it fall quickly. In a hover, you will be always moving the throttle tiny amounts. There is no stick position where it will stay at that altitude.

I actually have 3 of the eBay clone of those quadcopters.

It is very important to balance your props. If you have not balanced them, please do.

With battery and USB plugged in, go to Input page in GCS. Switch transmitter on. Do not arm. Move the throttle stick. You should be able to see the GCS Throttle slider move with the transmitter throttle stick. There will be a time lag (maybe one second) from when you move the transmitter stick to when you see the throttle slider move. Just make sure that a very low throttle stick makes a very low throttle slider. What would be bad is if the slider jumps way up with just a very small movement of the transmitter stick.

First of all, battery size: All of the following discussion assumes you are using a 3 cell LiPo. If you are running a 4 cell LiPo, the props should be about 2 inches smaller than I discuss.

motor and prop size: My small motors are 2212 (internal size) which are 2830 external size. The important thing is that they are KV1000. My large motors are 3530 external size and KV1100. I run 10x4.7 props on all of them. It looks like your motors are 2212 or maybe larger, that is OK. The KV is the important part. What is your motor KV? It also looks like you are running larger props than I am. If your motors are about KV800, I guess you should be running about 11x6 or 12x5 props. If your motors are about KV1000 you should be running about 10x5 (10x4.5 or 10x4.7) props. If your motors are KV1200, you should probably run 9 inch props. If your motors are KV1500 you should run about 8 inch props.

It looks like you are running perhaps 11 inch props (from what I see), and the prop pitch even looks fairly high, like maybe 11x6 size. 11x6 props are too big if your KV is 900 or higher.

ESC calibration: I assume that you are still running the settings in Aung2.uav, so the CC3D settings that relate to motor speed are OK. What I am going to suggest is dangerous if not done very carefully!!! I suggest that you tie it down like you did before. Leave the props on. Plug battery in. Plug GCS/USB in. Transmitter not needed. Go to Output page and click Test Outputs. Very carefully move one slider SLOWLY to the right until a motor starts. At any time you can press the Home key to move the current slider to the off position. (The End key is very bad. It moves the slider all the way to full power. Do NOT use it with props on!!!) When the motor starts it should be very slow. You should be able to slowly move the slider up about half way before it has enough power to lift that corner of the quad. Stop that motor (you can use the Home key for that( and test the other 3 motors the same way. If any motor is too fast at low speed, then you need to re run ESC calibration. You can also test all 4 motors at once. With all sliders all the way off (left), click the Link check box for each motor. Now you can slowly move one slider and all sliders will move. It should not take off till about one fourth of the way up. There is no stabilization when you test it this way.

The previous test shows if the ESCs are calibrated well enough to allow low throttle.

I see that the PIDs are slightly modified because of previous tests. You should probably set them back to default values, but I don't think that is your problem.

Calibrations: Has Level calibration (Attitude page) been skipped? That isn't your problem, but it shouldn't be skipped.

I will reply your discussion very detailed later,Here is my quick question...

I connect the wire as GCS said but when I searched on google and they did the other way... but differences is that they are using CC3D and I am using CC3D Atom... and different Reciever I am using FS iA6B

I connced the throttle wire which is 3wire (S, +, - ) to channel 3 because throttle is always on channel 3 right? And roll on ch 1, pitch on 2 and yaw on 4 etc...

So, here is my diagram of how I connected and What GCS showed and what I fond on google...

I connected the throttle wire which is 3wire (S, +, - ) to channel 3 because throttle is always on channel 3 right? And roll on ch 1, pitch on 2 and yaw on 4 etc...

When you run the setup program and wiggle each stick when it tells you to do so, it determines which wire does what. As long as GCS Input page (battery plugged in, USB cable plugged in, transmitter on) shows that each stick controls what it should control then it is correct.

You have used a manual throttle before and have practice that you must constantly adjust throttle by about 1mm or so? Sorry to ask.

What firmware are your ESCs running? If running stock firmware then there is an option for startup speed. SimonK and BLHeli firmware don't have this problem. Slow is used by one blade helicopters. Quad copters MUST use the fastest setting. You can test with props off (very very important) and "Test Outputs" as before. Press End and all motors should immediately be running at top speed. If even one motor takes much more than 1/2 second to get to top speed, then your ESC speed setting may be wrong.

I started thinking that my motor and props are not suitable I found on research that in 40% of throttle stick, drone start flying. My quad start take off just over neutral point and became hard to control. Can it be a reason of this problem?

With props too big, you get too much thrust at low throttle stick and no additional thrust at higher throttle stick. It also makes your motors and ESCs overheat and is less efficient than correct prop size so battery doesn't fly as long and motor/ESC might even fail from too much heat.

What parts do you have available? 8x5 props for these motors or 1000KV motors for the 10x4.5 props?

If you have a prop balancer, you could cut the tips off the 10x4.5 props to make them 8x4.5 (extra wide blade, so maybe even cut to 7.75x4.5 if motors get hot at 8x4.5). I cut 10x4.5 props down to 9x4.5 for one of my quads (F330).

Problem solved. Wrong motors and props.I was using 1400kv motors with 1046 props. I just recognized that the last time I built a quad with CC3D I used 1000kv now I choose 1400kv because It once worked well with QQ super controller. So, Indecided to change my motors. And after that when I tried. It didn’t flew away but don’t stable then. I just import the file that f5soh fixed of my original UAV file. And the quad flew like in the following video file